Add Clarity About Downloading and Self-Hosting a Font File (#33760)

Details about downloading and self-hosting font files were missing from our[ Font Optimization docs](https://nextjs.org/docs/basic-features/font-optimization). This PR addresses these changes.

## Bug

- [x] Related issues linked using #33054

## Documentation / Examples

- [x] Make sure the linting passes by running `yarn lint`

docs/basic-features/font-optimization.md

@@ -78,6 +78,8 @@ Automatic Webfont Optimization currently supports Google Fonts and Typekit with
 
 See [Google Font Display](https://nextjs.org/docs/messages/google-font-display) for more information.
 
+> **Note**: Font Optimization does not currently support self-hosted fonts.
+
 ## Disabling Optimization
 
 If you do not want Next.js to optimize your fonts, you can opt-out.